xhci: no switching back on non-ULT Haswell

The switch back is limited to ULT even on HP. The contrary
finding arose by bad luck in BIOS versions for testing.
This fixes spontaneous resume from S3 on some HP laptops.

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>